In a wireless communication system, such as a wireless local area network (LAN), wireless access points and wireless terminals perform wireless communication by using frequency channels. An arbitrary one of frequency channels available in the wireless communication system is assigned to each of the wireless access points. Hereinafter, a wireless access point may be described as an “AP”.
The number of the frequency channels available in the wireless communication system is limited; therefore, if a greater number of APs than the available frequency channels are present in the wireless communication system, in some cases, the same frequency channel may be assigned to a plurality of APs. If the same frequency channel is assigned to a plurality of APs, radio wave interference occurs among the plurality of APs, so that the throughput of the wireless communication system decreases. Furthermore, the radio wave interference among the APs increases or decreases along with a change in the wireless environment. Therefore, to reduce the radio wave interference among the APs, a “dynamic assignment method” has been proposed, in which frequency channels are dynamically assigned to the APs in accordance with a change in the wireless environment. Furthermore, as a technology related to the dynamic assignment method, for example, there is a technology to simultaneously assign frequency channels to all of the APs in the wireless communication system.
Related-art examples are described, for example, in Japanese Laid-open Patent Publication No. 2010-119087, and in Japanese Laid-open Patent Publication No. 10-079977.
In the above-described related technology, it is possible to simultaneously change the frequency channels of all of the APs in accordance with a change in the wireless environment. However, in the above-described related technology, the amount of calculations for assignment of frequency channels (hereinafter, may be referred to as an “assignment calculation amount”) exponentially increases in proportion to the number of APs present in a wireless communication system. For example, if C frequency channels are available in an environment in which N APs are installed in a wireless communication system, the number of calculation patterns for the assignment of frequency channels is CN. If the assignment calculation amount exponentially increases as described above, a calculation time for the assignment of frequency channels (hereinafter, may be referred to as an “assignment calculation time”) increases. If the assignment calculation time increases, it takes a long time to assign frequency channels after measurement of the wireless environment used as a basis for the assignment of frequency channels; therefore, an actual wireless environment at the time of the assignment of frequency channels may greatly differ from the wireless environment at the time of the measurement. If the actual wireless environment at the time of the assignment of frequency channels greatly differs from the wireless environment at the time of the measurement as described above, it is difficult to assign optimal frequency channels based on the actual wireless environment; therefore, the throughput of the wireless communication system decreases. That is, if the assignment calculation amount increases in assigning frequency channels based on the wireless environment, the throughput of the wireless communication system may decrease in some cases.